Neurophysiology III
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Questions and Answers

What type of nerve carries action potentials from the CNS to target organs?

  • Efferent nerve (correct)
  • Interneuron
  • Spinal nerve
  • Sensory nerve

    • The Golgi organ detects changes in muscle length.

    False

    What is the primary role of the sensory afferent nerve in the stretch reflex?

    To detect changes in muscle length and synapse with motor neurons.

    The _____ reflex involves contraction of the quadriceps muscle in response to tapping the patella ligament.

    <p>knee jerk</p> Signup and view all the answers

    Match the following components with their functions in the reflex arc:

    <p>Sensory neuron = Carries action potentials to the spinal cord Motor neuron = Conveys signals to target muscles Interneuron = Connects sensory and motor neurons Muscle spindle = Detects changes in muscle length</p> Signup and view all the answers

    Which of the following is NOT a component of a reflex arc?

    <p>Interneurons</p> Signup and view all the answers

    The reflex arc provides an involuntary and varying response to a stimulus.

    <p>False</p> Signup and view all the answers

    What is the role of proprioception in the reflex arc?

    <p>It provides sensory feedback about muscle tensions, joint angles, and body position to the CNS.</p> Signup and view all the answers

    The coordinating center of a reflex arc is located in the ______.

    <p>CNS</p> Signup and view all the answers

    What type of reflex arc is characterized by a direct connection between sensory and motor neurons?

    <p>Monosynaptic reflex</p> Signup and view all the answers

    List the five fundamental components of a reflex arc.

    <p>Sensory cells/receptors, sensory nerve fibers, coordinating center (CNS), motor nerve fibers, effectors (muscle or gland cells).</p> Signup and view all the answers

    Match the following components with their functions in a reflex arc:

    <p>Sensory cells/receptors = Transduce environmental stimuli into action potentials Motor nerve fibers = Conduct action potentials to effectors Effectors = Eliminate stimuli or perform a response Coordinating center = Integrate sensory input and elicit motor output</p> Signup and view all the answers

    The sensory (afferent) nerve carries action potentials towards the CNS.

    <p>True</p> Signup and view all the answers

    What is the role of muscle spindles in the stretch reflex?

    <p>Detect changes in muscle length</p> Signup and view all the answers

    The knee jerk reflex requires the contraction of both the quadriceps and the hamstrings simultaneously.

    <p>False</p> Signup and view all the answers

    What type of muscle fibers do sensory nerves contact to initiate muscle shortening?

    <p>Extrafusal alpha fibers</p> Signup and view all the answers

    Muscle contraction involves the pulling of the tendon and squeezing the bare end of the neuron, which acts as a _____ in the Golgi organ.

    <p>receptor</p> Signup and view all the answers

    Match the following reflexes with their primary features:

    <p>Knee jerk reflex = Quadriceps contraction in response to patella tapping Tendon reflex = Inhibition of muscle contraction due to excessive tension Stretch reflex = Activation of motor neurons for muscle shortening Golgi organ reflex = Prevention of tendon injury from excessive load</p> Signup and view all the answers

    What is the main function of the reflex arc?

    <p>To provide an automatic or unconscious response to a stimulus</p> Signup and view all the answers

    The five components of a reflex arc include only the sensory and motor nerves.

    <p>False</p> Signup and view all the answers

    What is the role of proprioception in the reflex arc?

    <p>To provide sensory feedback on the position and movement of body parts.</p> Signup and view all the answers

    The __________ reflex arc involves a direct connection between sensory and motor neurons.

    <p>monosynaptic</p> Signup and view all the answers

    Match the components of the reflex arc with their descriptions:

    <p>Sensory cells = Transduce environmental energy Motor nerve fibers = Conduct APs to effectors CNS = Coordinates the reflex response Effectors = Muscle or gland cells responding to APs</p> Signup and view all the answers

    Which structure is NOT involved in the control of body movement?

    <p>Thalamus</p> Signup and view all the answers

    Malfunction of any component of the reflex arc can alter the reflex response.

    <p>True</p> Signup and view all the answers

    What type of information do proprioceptors send back to the CNS?

    <p>Sensory information about muscle tension and joint angles.</p> Signup and view all the answers

    Study Notes

    Levels of Movement Control

    • Three levels of control higher, middle and lower
    • Higher centers - cerebral cortex (conscious)
    • Middle level
      • Sensorimotor cortex
      • Cerebellum (monitors execution)
      • Basal ganglia (semi-voluntary movements)
    • Lower level - Spinal cord from which motor neurons exit (site of somatic reflex arcs)

    Reflex Arc

    • Five key components
      • Sensory receptor
      • Sensory nerve
      • Coordinating center (CNS)
      • Motor nerve
      • Effector (muscle or gland)

    Somatic Reflex Arcs

    • Receptors
      • Convert environmental energy into action potentials (APs)
      • Frequency of APs proportional to intensity of energy (frequency coding)
    • Sensory (afferent) nerve
      • Conducts APs from receptor
      • Cell body located in ganglion
      • Enters spinal cord via dorsal roots
    • Coordinating center
      • Synapses within the CNS
      • Monosynaptic (muscle spindle reflex)
      • Multisynaptic (elaborate reflexes)
    • Motor (efferent) nerve
      • Carries APs from CNS to target organ
      • Via ventral roots
      • Cell body located within the CNS
    • Target organ
      • Response may involve skeletal muscle e.g. knee jerk or multiple targets e.g. scratching

    Stretch and Tendon Reflex

    • Monitors muscle length and tension
    • Muscle spindles
      • Specialized muscle fibers
      • Sensory nerve activated by stretching of muscle spindle
      • Activate motor neurons of the same muscle
      • Causes muscle contraction, shortening the muscle
    • Golgi tendon organ
      • Located in tendons
      • Senses tension in tendons
      • Activates inhibitory interneurons in spinal cord
      • Inhibits motor neurons serving the same muscle
      • Prevents excessive muscle tension

    Antagonistic Muscle Groups

    • Muscles work in pairs
    • One muscle contracts, the other relaxes
    • Example - Biceps and Triceps
      • When biceps contracts, the triceps relaxes
      • Allows for smooth and controlled movement

    Knee Jerk Reflex

    • Protective reflex
    • Tapping the patella ligament stretches the quadriceps tendon
    • Activates sensory neurons in the muscle spindle
    • Activates motor neurons of the quadriceps muscle
    • Causes the quadriceps muscle to contract
    • Briefly extends the leg

    Calf Case Study

    • 2-month-old calf with hind leg lameness
    • No withdrawal response in hind legs
    • Loss of proprioception in hind legs
    • Diagnosis: Cord compression due to abscess in vertebral body (often level L4)

    Levels of Control of Body Movement

    • Three levels of control: higher, middle, and lower
    • Higher Centers: Cerebral Cortex (conscious)
    • Middle Level: Sensorimotor cortex, cerebellum, and basal ganglia
    • Lower Level: Spinal cord, site of somatic reflex arcs

    Components of a Reflex Arc

    • Automatic, unconscious response of effectors organs
    • Involuntary and unvarying response
    • Five components: sensory cells/receptors, sensory nerve fibers, coordinating center (CNS), motor nerve fibers, effectors (muscle or gland cells)

    Somatic (Skeletal Muscle) Reflex Arcs

    • Transduce environmental energy: skin, muscle, tendons
    • Convert energy into action potentials (APs)
    • Frequency of APs proportional to intensity of energy

    Stretch and Tendon Reflex

    • Changes in muscle length detected by muscle spindles
    • Changes in tendon length detected by Golgi organ

    Knee Jerk Reflex

    • Quadriceps muscle contraction in response to "tapping" of the patella ligament
    • Brief leg extension
    • Requires relaxation of opposing flexor muscles (via activation of inhibitory interneurons)

    Calf with Neurologic Abnormalities

    • 2-month old calf, gradual onset of hind leg lameness
    • Examination: no withdrawal responses in hind legs, weakness, poor muscle tone, loss of proprioception
    • Problem: cord compression, abscess of vertebral body (L4)

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    Related Documents

    Neurophysiology III: Reflex Arcs Lecture Notes PDF

    Description

    Test your knowledge on the three levels of movement control, from higher centers in the cerebral cortex to lower spinal cord functions. Explore the components of somatic reflex arcs and their significance in the nervous system. This quiz will challenge your understanding of how sensory and motor pathways interact.

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